DNA test
Being more close and thus similar to her mother than an average, Yvonne was more likely to replace her. Paradoxically, one can use this very fact to check if the switch took place using only the cells from one of them. Here is a website with predictions for the outcome of such test. From the paper "A Bayesian Assessment of the Longevity of Jeanne Calment" Although our calculation gives a 99.99% chance of an identity switch in the case of Mme Calment, we acknowledge the subjective nature of this result. We expect that some other investigators will not agree with our figures. An objective test is therefore needed to settle the question of Mme Calment’s longevity validation. This is possible using DNA sequencing. We know that Jeanne Calment and Fernand Calment were double second cousins. We have verified this ourselves by searching through all the relevant acts of birth, marriage and deaths. We find the vital details to be unambiguous unless an earlier falsification took place. This means that Yvonne was the product of in-breeding between her parents with 5th degree consanguinity. This would result in detectable autozygosity in her DNA characterised by long runs of homozygous genes. On average one in 32 allele pairs in her genome would be inherited from the same common ancestor. Normal levels of recombination in autosomes means that these homozygous genes occur in long runs of homozygosity (ROH) which can be detected and counted once the genome has been fully sequenced. For the level of consanguinity between Yvonne’s parents, the actual count should be around 2 to 5% of the genome. DNA tests now in use can distinguish counts as low as 1% from background. To complete the test a number of laboratories should independently measure the FROH (fractional ROH) from SNP data for all the autosomes with a range of threshold sizes e.g. 1Mb and 8Mb. Jeanne had no known common ancestors, so with a single test of Mme Calment’s DNA it should be possible to settle the question of her identity with a high degree of confidence 27. Other DNA tests could be used such as consanguinity with known living blood relatives of Yvonne who are not blood relatives of Jeanne. In particular, there are several living descendants of Emile Fassin, the former mayor of Arles who married Anne Felix, the sister of Yvonne’s paternal grandmother. Some are second cousins once or twice removed from Yvonne Calment, but have no close blood relation to Jeanne Calment. A test based on complete DNA sequencing can easily distinguish this relationship. This will be largely independent of the autozygosity test which uses lines of ancestry passing through Yvonne’s mother and her paternal grandfather. Measurements of the epigenetic clock could also be attempted but this may require a control study of other supercentenarians 28. We understand that the Jean-Dausset foundation in Paris holds suitable bio-samples from Mme Calment that could be used for this purpose if legal barriers can be removed. There is also a possibility that stamps on letters sent by Mme Calment to relatives could yield DNA samples. We understand that French law is strict on the use of DNA testing but tests for scientific purposes are permitted. A legal decision may be required to determine if this use of the DNA is possible under the privacy conditions it was given. We urge the gerontological community of France to support organisation for this to be carried out. According to Jeanne Calment’s validator Jean-Marie Robine, she eagerly accepted brain imaging and blood tests to investigate her longevity 29-33. There may be ulterior interests in the DNA of Mme Calment from researchers working on the genetics of longevity. We understand that this leads to suspicions about motives for the DNA tests especially where financial gain may be possible. We, the authors of this paper, wish to make it clear that we have no conflict of interest of this type. We are happy for any tests to be carried out by agents independent of any interested parties. This would be under conditions that would only reveal the derived numbers necessary for the tests described here to establish the identity of Mme Calment. There should be control samples tested blindly alongside Mme Calment’s sample. The tests should be performed by at least three laboratories not linked to each other to ensure reproducibility. Although we would require the genome of Mme Calment to be fully sequenced, we do not require it to be published or made available to ourselves or anyone other than the independent agents. The possibility of scientific tests for other purposes is a separate matter and is not our interest. We appeal to French gerontologists and the family of Mme Calment to support these DNA tests under conditions that they are free to propose. Only this will return the certainty that science and her family need to understand the life of this remarkable woman.